We have initiated collection and storage of specimens to evaluate changes in ovarian morphology, serum estrogen, bone density, and DNA deletions over time in female rhesus monkeys. Preliminary measurements of bone strength from young monkeys 3-5 years of age and aged monkeys 22-25 years demonstrate that breaking strength of femurs decreases substantially with age. Young monkey femur strength was 13.5 MPa (comparable to a previous report by Yamada, 1970) while aged monkey femur strength averaged 9.7 MPa, about 70% less. Thickness of cortical and trabecular bone decrease with age while the number of trabecular intersections increases. Similar measurements using the wing of the pelvis (iliem) failed to demonstrate these correlations. Enumeration of eggs, primary follicles and cystic follicles in histologic sections of ovaries showed substantial decreases with age. The results should provide a basis for study of aging females from puberty through menopause.